This invention relates to clutch mechanisms. More particularly, the invention relates to a clutch mechanism of the type employing a torsion spring adapted to frictionally engage and disengage a rotating spindle. The invention is particularly applicable for use wherein controlling the angular position of a pivotable member is required, such as an automotive reclining seat back.
In the field of reclining seats, it is highly desirable to provide for adjustment and retention of the seat back at any of an infinite number of angular positions between the extreme upright and reclined positions. Further, it is well known that automotive seat backs are subjected to very high forces in use, particularly in regard to rearwardly directed forces due to, for example, inertial forces developed in vehicle rear end impacts as well as user initiated forces.
Heretofore, infinitely adjustable clutch mechanisms have not been totally acceptable for automotive reclining seat applications for at least two principle reasons. First, although spring clutches have been devised that provide infinite angular positioning, such as that disclosed in my U.S. Pat. No. 4,573,738, they have required the use of two oppositely wound tandum springs so that loads imposed thereon in opposite directions of rotation may be equally absorbed. This has been the case because single spring clutches have heretofore offered high frictional holding power in only one direction of application of force. Prior to the present invention, spring clutches have had less holding power when forces are applied in the direction which tends to unwind the spring coil because the spring is caused to unload. This is true because the principle of operation of a spring clutch demands that one end of the spring coil must be fixed against movement and the opposite end of the spring coil must be free to move so as to allow the coil of the spring to always be in tension under the influence of the particular external force imposed thereon, thereby preventing the spring coil from buckling and unloading.
Heretofore, there has been no structure devised for selectively fixing the ends of the spring coil so as to provide for the required movement and affixation depending on the direction of application of the external force thereon so as to maintain the spring coil in tension regardless of the direction of application of the external force.
To overcome this shortcoming, two torsion coil springs, either wound in opposite directions or mounted with their windings orientated in opposite directions, have been employed so that one spring aborbs forces in one direction and the second spring aborbs the forces in the opposite direction. While these structures provide for equal holding power regardless of the direction of application of the external force, they require an additional clutch spring and related components which is not cost or space efficient.
It can, therefore, be appreciated that it would be highly desirable to provide for a single torsion spring clutch mechanism that provides for equal holding power in each of opposite directions of rotation of a spindle under the influence of externally applied forces on a pivotable member such as a reclining seat back which is connected to the spindle and which further provides for infinite angular adjustment and retention of the member at all locations between its extreme angular positions.